Hydroxypropylation of Sorghum Starch: A Potential Excipient in Drug Formulation

Hydroxypropylation of sorghum starch for a potential pharmaceutical application as an excipient in tablet formulations was carried out. The starch was chemically modified via hydroxypropylation and characterized by SEM, XRD and FTIR. SEM showed irregular shape while the modified starch has regular shape and fibrous long distort shape. The XRD revealed the native and modified starches are completely amorphous in nature as there were no sharp peaks observed. The FTIR spectra showed broad band located within the region 3800-3500cm-1 which appeared in the native and modified starches indicating the free OH stretching vibration as well as intra-molecular hydrogen bonding in starch molecules. The major functional groups in the native starch were 1736cm-1 (C=O), 1625cm-1 (-COO-), 1427cm-1 (-COO-), 1227cm-1 (-C=O-), 1162cm-1 (C-O stretching and C-H stretching). During hydroxypropylation there were introduction of new functional groups observed at 1800-1500cm-1 (-COO-) and 1606-1632cm-1 (OCH2COONa) respectively. The moisture content of the native starch was 5.46±0.00 and modified Starch was 4.82±0.01 . The pH of the native and hydroxypropyl starch were 7.00±0.01 and 7.29±0.02 respectively. Relative viscosity value of 1.70±0.08 and 2.76±0.00 were observed for the native and modified starches respectively. Water holding capacity of the native and modified starches were 28.35±0.20 and 33.25±0.01 respectively. The flow properties of the starch granules show low angles of repose, high flow rate which fall within hausner ratio and carr’s index for tablet formulation. Hence, Modification of native sorghum starch by hydroxypropylation shows better physicochemical properties than the native which enhanced a better efficacy in the tablet granule and flow properties in drug formulation.